For the past two and a half years, Bradley Manning, the soldier accused of giving hundreds of thousands of classified documents to Wikileaks, has been the quiet enigma at heart of the largest and most contentious intelligence leak case in American history. As I write in “The Trials of Bradley Manning,” my story for the latest issue of Rolling Stone, this silence – imposed by a lengthy pretrial detention that included nearly a year spent in “administrative segregation,” the military equivalent of solitary confinement – made it possible for a legion of interested parties on both sides of the political spectrum to graft their own identities and motivations onto Bradley Manning. They have portrayed him variously as a hero, a traitor, an emotionally-troubled misfit and a victim of prison abuse.

This morning, February 28th, Bradley Manning finally had a chance to define himself. He appeared before a military judge at Ft. Meade, Maryland, to publicly accept responsibility for being the source of the Wikileaks documents and plead guilty to roughly half of the 22 charges against him, for which he could receive a maximum sentence of 20 years. It was only the second time Manning had spoken in court (the first, in November 2012, I detail extensively in my article) and the first time he was allowed to explain his motives. Dressed in his Navy blue Army dress uniform, Manning, in a clear, strong voice, read out a 35-page-long statement in which he described himself as a conscience-stricken young man who, appalled by what he saw as illegal acts on the part of the U.S. in Iraq and Afghanistan, refused to play along. (Read Manning’s full statement as transcribed by journalist Alexa O’Brien.)

“Depressed with the situation we were mired in [in Iraq],” and dismayed by counterterrorism operations in which the U.S. seemed “obsessed with capturing and killing people,” Manning said he’d sought to “make the world a better place” and spark a national debate over the military’s role in U.S. foreign policy by releasing the trove of “war logs” from Iraq and Afghanistan – a tremendous cache of military communiques which detailed a range of missteps. “We were risking so much,” he said. “I wanted people to know that not everyone [in Iraq and Afghanistan] were targets to neutralize.” He took pains to review the categories of information he found, eliminating those he thought might harm U.S. national security, and choosing only those he thought would “embarrass” the country, notably the roughly 250,000 diplomatic cables revealing “back room deals” that “did not seem characteristic of [a country that was] so-called leader of the free world.”

The most shocking admission of the morning was Manning’s contention that prior to contacting Wikileaks, he’d tried to go the conventional route, attempting to leak the information to the mainstream media. While on leave in the winter of 2010 at his aunt’s house in Washington, D.C., Manning had phoned The Washington Post, hoping to give them the logs, but the editor or reporter he spoke to “didn’t take me seriously,” he said, and the call went nowhere. So Manning next tried the public editor at The New York Times, leaving a phone message that he said was never returned. He then considered Politico, but was thwarted by the huge winter storm, known as “Snowmageddon,” that blew across the east coast at just this time, crippling the nation’s capitol, and its transportation system, for several days.

Only then did Manning turn to Wikileaks, uploading the first of the leaks – the Iraq and Afghan War Logs – from his laptop while at a Barnes and Noble in suburban Rockville, Maryland. Wikileaks would later make its reputation on these documents, notably the 2007 video of a U.S. Apache helicopter attack on Iraqi civilians, which Manning referred to as “war porn.” What disturbed him most, he said, was the “bloodlust” exhibited by the Apache team, whose behavior struck him as similar to “a child torturing an ant with a magnifying glass.”

Over the coming months, Manning would have numerous secure online conversations with someone at Wikileaks he knew only as “Nathaniel” – presumed to be either Julian Assange or Assange’s onetime colleague and Wikileaks cofounder, Daniel Domscheit-Berg. In an exclusive interview with Rolling Stone, Domscheit-Berg admitted that he’d had several interactions with a person now believed to be Manning. “Whoever this person was, he was someone with good intentions,” Domscheit-Berg told me. “He was appalled by what was happening and felt helpless about what to do about it.”

Manning has often been cast as a naïve young man who was manipulated by Assange, Berg or others into giving them the information. In accepting his guilt, he made it clear that no one pressured him into doing it. “The decision to send was my own,” he said. “And I take full responsibility.” But the case against Manning is far from over. He still faces the most serious charges, including “aiding the enemy” and others that fall under the Espionage Act, for which he might still receive a life sentence if convicted.

For the full story of how Bradley Manning reached this point – and what happened to him as a result of his actions – read “The Trials of Bradley Manning” in the latest issue of Rolling Stone.